Radio system for distance measurement



April 8, 1952 P. A. PERILHOU 2,592,459

RADIO SYSTEM FOR DISTANCE MEASUREMENT Filed Sept. 24, 1948 Patented Apr. 8, 1952 nAmosrsrrEM For, DISTANCE MEASUREMENT APierre Andrlerilhou, Clamart, `France,assigner "to "O'fdce :National YdEtudes *et 4de `Recherches Aeronautiques,"Paris, France, la -company of France Application September 24, 1948, Serial No. 51,030 f In France September-25, `19477 V:8 Claims.

'I'hislinvention relates to theprblem of controlling the reception Aoffradio electric apparatus and-has for its object amethod and means .permitting to maintain the'level cfa receptionbetween predetermined limitsin spite of variations of-an incoming e'ld in certain-conditions of use.

The invention is .applicable ymore particularly to the eld of ultra short `waves and namely to receiver apparatus used in relation'with Yradio beacons of la rotating beamtype or the'lke with a view to render the output voltage of such receiver apparatus' independent of variations of distance-between such an apparatus andthe radio beacon.

In -an application of a radio 'beacon o`f such a type to the` guiding of dirigible craft, ithas been suggested to use the timeinterval between the instants of reception of abeam of radiant` energy angularly movable in azimuth by two separate receiving aerials spaced apart a certaindistance, for determining the'range 'betweenthe base 'of reception constituted 'by these two vaerials and the radio beacon.

As the" eld `intensity of ltransmittedV radiations varies with'distance of the receiving point 'to .the transmitter, a measure of distancemay-.serveor controlling the reception so 'as' to maintainv the level 'of "the same substantially 'independent of zdistance;

Accordingly, vthe inventionbroadly consists in a `novel method of automatic volume control "of a receiver `apparatus according to which the level of reception of such van apparatus is controlled in accordance with a'measure of distance between A .said apparatus and the `'.'transmitter of incoming radiations.

`More particularly the invention contemplates the vapplication of the above principle to receiver 4equipments incorporating'or used inconjunction `with distance measuring arrangements, and especially'those ofthe very high frequency type.

Asa particular case of such'applications. Athe Yinvention contemplates furthermore -a receiver 'equipment of the-above mentioned type'comprlsing at -least two spaced and independent receiv- Yingaerials intendedior operation in conjunction `with a radio beacon of the type producing a beam of radiant energy and namely of avery high frequency presenting a variable characteristic in azimuth, invor'der Ito provide an indication of distance Vof .a craft with respect :to `said 'beacon `and/or guide theisame ftowardfsaid ibeacon.

According to-a'further feature Vofithe invention, the :level .fof reception ,of suchian apparatus is. controlled zas function ofr'aztime'fdierencetbetween instants of reception of a said beam of 2 radiant energy by'two'aerials spacedvapart "a ,predeterminate known fdistance.

In accordancewith 'an other feature or lthe invention, the automaticvolume :control -is yper- 'fected by .biasing an amplifier "andnamely'the rst tube of a receiver channel by a voltagewhich varies as a `function of'a measure 'rofdistance and in the 'particular case L'of Lthe above lmentioned apparatus, `by Va time lag *between `rthe instants of reception 'of Yincoming radiations by tWo' spaced .receiving "iaerials According to another :feature of the" invention, the above mentioned 'control of Jreception Amay be produced'by detuninjg or varying the coeicient Of'overevoltage ofaresonantA volume `ofy areceiver channel as 'a `function' of4 a`voltage yproportional to a measure of distanceoragaininthe tcase of ,the above mentioned equipment .bythetime lag between pulses .in'ducedbya rotating or like'beam of radiantenergy Aupon its passage by two spaced aerials, this voltage 'giving the measure of ldistance.

L"Theaboveand otherobjects'and features `of the invention will appearclearlyffromthe following Ldescription and the annexed drawings, it being understood that'these drawingssare given for f the 'purpose of `illustration of the "invention only andl are not limitative Vwith regards 'to the scope V'of the. invention.

On the drawings:

.Figy'l shows a schematic representation-ofthe -use vvof a 'radio beacon of ia rotatingbeamtype .'inconjunction "with a receiving Dassembly "compri'sing' two spaced vaerialspermittingto measure fthe distance separating 'thepoin't of origin ofthe J'radio beam 'and 'thepoint at Whichis located said base ofreception.

Figfzshows a block diagram oran apparatus or A equipment vconstituting an embodiment' ofthe invention.

`Fig.Y 3' represents a vportion YofA a blockV diagram similar to that of Fig. 2fz-and illustrates a different embodiment of the invention.

Referring now to Fig. l there is shown in l a directive beam of ultra high frequency radiations 'produced' by a vrotating radio beacon (not shown) "located at `point O. Thisbeam is characterized `by`a beam width H and-is rotated 'in azimuthat a uniform speed w about the point of origin'O. :At-point M, on axis'OX, there is shown a receiv- -ing :equipment comprising two Aaerials Anand B :arranged symmetrically on either .sidesof .axis

v(3M at Vthe .opposite 'extremitiesofeabaseiine vperpendicular nto said axis, :said equipment rperl.mitting .to measure `the distance .between points M and O. This receiving equipment may be car- 3 ried by a dirigible craft and in such a case may serve for measuring the distance of said craft to the radio beacon I. This measure of distance is based on the measure of the time spacing between the instants of reception of the rotating beam by the two aerials,said time spacing being expressed by a variable voltage depending on said distance, in accordance with a disclosure of aA In the above mentioned and similar applica# tions of radio beacons and more particularly of a rotating beam type, it is always interesting to obtain the desired indications at the greatest possible range so that the over voltage coefficient of resonant volumes used in such receivers must have the maximum value. However, with a decrease of the distance between a craft and a radio beacon or in general a transmitter, the voltage applied to resonant volume devices becomes rapidly excessive for a proper operationv of Crist-als of said devices and consequently this creates a necessity to reduce such a voltage as the craft approaches to the radio beacon or a transmitter.

As on the other hand the use of known arrangements of automatic volume control based on a measure of the reception level presents certain difficulties and drawbacks as regards interference and setting in of oscillations, it is suggested, according to the invention, to effect an automatic volume control in a receiver and more particularly of the type specified, in response to a measure of the distance between the craft and the transmitter of incoming radiations.

This invention is especially applicable to apparatus or equipments including distance measuring provisions or devices such as more particularly described in copending applications Serial No. 50,515, led on September 22, 1948, entitled "Improvements in Distance .Measuring Systems, and Serial No. 50,514, filed on September 22, 1948, entitled Improvements in Systems for Guiding Dirigible Crafts.

In accordance with said applications, one provides as shown in Fig. 1 at the receiving end for instance on a dirigible craft, two independent aerials A and B spaced apart a predetermined distance. These aerials may be constituted by dipoles associated with resonant volumes 2 and 2 as shown on Fig. 2. The passage of a rotating beam such as I on Fig. 1 on two aerials A and B induces in said aerials two signal voltages displaced in time one with respect to the other by a quantity defined by the following equation:

d I D21r'w in which:

d is thev spacing between two aerials A and B, D is the distance between the point of loca'- tion of the radio beacon and the point of location such as M of aerials A and B and w is the angular speed of rotation of the beam.

filed on September 242, 1948, and entitled` Improvements in Distance Measuring Systems and which is used for providing an indication of distance D.

According to the present invention, it is suggested to ,use such or a similar indication of measure of distance for effecting an automatic volume control of a receiver equipment and more particularly of an equipment providing such a measure of distance separately or in conjunction with .other indication permitting to de- Y termine the azimuth of a craft or to guide the lfollowed by receiving 'channels each comprising an amplifier 3-,3",' a'ilter 444', a limiter 5--5 anda differentiator E--6'. The outputs of said channels' areconnected to the input of a mixer 'i followed by pulser 8, a second filter 9 and'a corrector l0, this latter feeding an indication apparatus not shown." The operation of this equipment corresponds to that described in the copending application Serial No.V 50,515, filed on September- 22, 1948, and entitled Improvements Vin Distance MeasuringSystems and needs not to be described in detail here. It will be'suflicient to state that signalsinducedin the aerials A and BV after an ,amplification are indexed in relation to time by locally produced short duration pulses corresponding to a certain point of each signal curve determined by a certain signal level having a predetermined relation to the maximum level of said signals. These locally produced pulses are introduced into the mixer and are used to produce a voltage proportional to their spacing in time which constitutes the measure of distance .ofthis'equipment to the radio beacon.

According to the invention, to provide an automatic" volume control of such an equipment,

it is suggested to use the distance indicating voltage at vthe output of corrector l0 to control an element of the receiving channels corresponding to the two aerials, represented by the lines II and ll.,

Thisvoltage may be adapted to act directly on the bias of a first amplifier tube 3-3 in each channel, as shown in Fig. 3, or on a resonant cavity such as 2 2', of said channels, as shown in Fig. 2, so-as to detune the same when the receiving base line AB is approaching the point O, that is when the interval of time between the received signals and consequently the mean voltage at the -output of corrector I0 increases. I This method permits thus to protect detector crystals of resonant volumes against excessive voltages, while avoiding any risk of interference or setting in of oscillations by eliminatingthe use of a closed circuitcontrol pres- -ently usedin known Asystem for producing such I claim:

1. In a system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth, means for receiving said beam at another point, said latter means comprising at least two independent aerials spaced transversely and symmetrically with respect to a straight line joining the two points, means for combining the effects of reception of said beam by said aerials so as to provide an indication of distance by a value of a current voltage depending on the time spacing of equivalent phases of said effects of re-l ception and means for controlling the level of reception of said energy receiving means in response to the value of said current or voltage to maintain said level substantially independent of distance.

2. In a system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth, means for receiving said beam at another point, said latter means comprising at least two independent aerials spaced transversely and symmetrically with respect to a straight line joining the two points, means for comparing in relation to time the equivalent phases of reception of said rotating beam by said aerials so as to provide an indication of distance as a function of time spacing of said phases of reception, means for producing in response to the time comparison of the equivalent phases of reception of said rotating beam by said aerials to provide a current or Voltage giving a measure of distance between the two points and means for controlling the level of reception of said energy receiving means in response to said current or voltage.

3. In a system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth, means for receiving said beam at another point, said latter means LVcomprising at least two independent aerials spaced transversely and symmetrically with respect to a straight line joining the two points, means for indexing in relation to time signal curves of reception of said beam by said aerials by locally produced sharply deiined pulses corresponding to a point on said curves determined by a certain level of said signals having a predetermined relation to the maximum level thereof, means for combining said locally produced pulses so as to provide an indication or measure of distance by a value of a current or voltage depending on the time spacing of said pulses and means for controlling the level of reception of said energy receiving means in accordance with said current or voltage.

4. In a system for distance measurement comprising means for transmitting from one point a beam of radiant energy adapted to rotate in azimuth, means for receiving said beam at another point, said latter means comprising at least two independent aerials spaced transversely and symmetrically with respect to a straight line joining the two points, means for indexing in relation to time signal curves of reception of said beam by said aerials by locally produced sharply defined pulses corresponding to a point on said curves determined by a certain level of said signals having a predetermined relation to the maximum level thereof, means for comparing in relation to time said locally produced pulses so as to provide an indication of distance by the time spacing of said pulses, means for producing a current or voltage proportional to the time spacing of said pulses and means for controlling the level of reception of said energy receiving means in response to said current or voltage.

5. In a system for guiding a dirigible craft toward a given point, a distance measuring equipment comprising means for transmitting from said point wave energy radiations presenting a characteristic variable in azimuth, and means for receiving said radiations on the dirigible craft, said latter means comprising at least two independent aerials spaced transversely to said craft, means for combining the effects of reception of said aerials to produce an indication of distance of the craft to said point and means for using said measure of distance to control the level of reception of said receiving means to compensate for the variation thereof in accordance with variation of said xdistance.

6. A receiver apparatus for a dirigible craft permitting to measure distance of said craft to a given point comprising at least two independent aerials spaced transversely to said craft and adapted to cooperate with a beacon located at said point and transmitting wave energy radiations presenting a characteristic variable in azimuth, separate receiver channels associated with each of said aerials, common receiver means connected to said channels for combining the effects of reception of said aerials to produce a voltage giving a measure of distance of the craft to said point and means for controlling said separate receiver channels corresponding to said aerials by said voltage so as to render the effects of reception of said aerials independent of said distance.

7. A receiver apparatus according to claim 6 wherein the spaced aerials are adapted to c0- operate with the wave energy transmitting beacon to produce a measure of distance and an indication of directional guidance of the craft toward said beacon and in which said measure of distance is applied to control said receiver means to maintain the level of reception independent of distance.

8. A receiver apparatus permitting to measure distance of a dirigible craft to a given point comprising at least two independent aerials spaced transversely to said craft and adapted to cooperate with a beacon located at said point and producing a beam of radiant energy rotating in azimuth about said point, receiver means associated with said aerials for determining the time spacing between signals induced by said beam in said aerials upon its passage by said aerials, means for translating said time spacing into a voltage or current of a corresponding value representing the measure of distance of the craft to the point of location of said beacon and means for applying said voltage to control said receiver means to maintain the level of reception independent of distance.

PIERRE ANDR PERILHOU.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,999,047 Hahnemann Apr. 23, 1935 2,034,520 Leib Mar. 17, 1936 2,051,966 Runge Aug. 25, 1936 2,307,023 Cooke et al Jan. 5, 1943 2,439,044 Ferrill Apr. 6, 1948l 

